package com.ocm.tourism.file;

import java.awt.Dimension;
import java.io.IOException;
import java.io.InputStream;

public class SimpleImageInfo {

   public static Dimension processStream(InputStream is) throws IOException {
      int height;
      int width;
      String mimeType;

      int c1 = is.read();
      int c2 = is.read();
      int c3 = is.read();

      mimeType = null;
      width = height = -1;

      if (c1 == 'G' && c2 == 'I' && c3 == 'F') { // GIF
         is.skip(3);
         width = readInt(is, 2, false);
         height = readInt(is, 2, false);
         mimeType = "image/gif";
      } else if (c1 == 0xFF && c2 == 0xD8) { // JPG
         while (c3 == 255) {
            int marker = is.read();
            int len = readInt(is, 2, true);
            if (marker == 192 || marker == 193 || marker == 194) {
               is.skip(1);
               height = readInt(is, 2, true);
               width = readInt(is, 2, true);
               mimeType = "image/jpeg";
               break;
            }
            is.skip(len - 2);
            c3 = is.read();
         }
      } else if (c1 == 137 && c2 == 80 && c3 == 78) { // PNG
         is.skip(15);
         width = readInt(is, 2, true);
         is.skip(2);
         height = readInt(is, 2, true);
         mimeType = "image/png";
      } else if (c1 == 66 && c2 == 77) { // BMP
         is.skip(15);
         width = readInt(is, 2, false);
         is.skip(2);
         height = readInt(is, 2, false);
         mimeType = "image/bmp";
      } else {
         int c4 = is.read();
         if ((c1 == 'M' && c2 == 'M' && c3 == 0 && c4 == 42) || (c1 == 'I' && c2 == 'I' && c3 == 42 && c4 == 0)) { // TIFF
            boolean bigEndian = c1 == 'M';
            int ifd = 0;
            int entries;
            ifd = readInt(is, 4, bigEndian);
            is.skip(ifd - 8);
            entries = readInt(is, 2, bigEndian);
            for (int i = 1; i <= entries; i++) {
               int tag = readInt(is, 2, bigEndian);
               int fieldType = readInt(is, 2, bigEndian);
               // long count = readInt(is, 4, bigEndian);
               int valOffset;
               if ((fieldType == 3 || fieldType == 8)) {
                  valOffset = readInt(is, 2, bigEndian);
                  is.skip(2);
               } else {
                  valOffset = readInt(is, 4, bigEndian);
               }
               if (tag == 256) {
                  width = valOffset;
               } else if (tag == 257) {
                  height = valOffset;
               }
               if (width != -1 && height != -1) {
                  mimeType = "image/tiff";
                  break;
               }
            }
         }
      }
      if (mimeType == null) {
         throw new IOException("Unsupported image type");
      }
      Dimension dimension = new Dimension(width, height);
      return dimension;
   }

   private static int readInt(InputStream is, int noOfBytes, boolean bigEndian) throws IOException {
      int ret = 0;
      int sv = bigEndian ? ((noOfBytes - 1) * 8) : 0;
      int cnt = bigEndian ? -8 : 8;
      for (int i = 0; i < noOfBytes; i++) {
         ret |= is.read() << sv;
         sv += cnt;
      }
      return ret;
   }
}
